Method and apparatus for forming motor winding conductors

ABSTRACT

Method and apparatus for forming motor winding conductors rectangular conductor wire. The method comprises populating with hairpin shaped conductors, most of a forming fixture having a plurality of pockets distributed in equal number in one or more pairs of adjacent circles, each concentric with a center of the forming fixture, at least one member defining each of the pockets in one of each pair of adjacent circles being rotatable, at least through a limited angle, with respect to a member defining the pockets in the other of the respective pair of adjacent circles, the hairpin conductors each having first and second legs integrally joined by a loop at one end thereof, with one leg of each hairpin conductor in a respective one of the pockets in a pair of adjacent circles, and rotating in a first direction, relative to each other, the members defining the pockets in each pair of circles through a predetermined angle, to permanently separate the two legs of each hairpin conductor without substantial rotation of each leg of the hairpin conductors relative to its respective pocket. Various additional features are disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of electric motors.

2. Prior Art

Tecnomatic S.p.A., assignee of the present invention, has in the pastmade a limited number of motor motors and D.C. motor rotors using flator square wire for the windings. In that regard, it is to be noted thatas used herein, “flat” or “square” wire means wire having foursubstantially flat sides, each joined to adjacent sides, typically by arounded edge. In the case of square wire, the wire may be formed in thesquare shape and then coated with typical winding insulation, or in somecases, pre-coated round wire has been rolled into the square shape.Rolling of round wire to a square shape has definite limits if theinsulation is not to be damaged, though smaller rounded edges may beachieved if the wire is first formed by drawing or otherwise formed intothe square shape and then coated. Even if the wire is first formed inthe desired shape and then coated, some degree of rounding on the edgesis desired for various reasons, including prevention of surface tensionfrom pulling the coating away from the sharp edges during coating,preventing the sharp edges from cutting through the coating afterward,and preventing electric field concentration on the sharp edges to induceearly breakdown. Thus, as used herein, the words “square”, or “flat” orequivalent words used to describe the cross-section of an insulatedcopper wire are used in the general sense and are not to be construed asexcluding significant or substantial rounded corners joining thesubstantially flat sides. “Flat” as used herein and in the claims meanshaving two opposite sides having a greater separation than the other twoopposite sides, its width being greater than its thickness. “Straight”as used herein and in the claims means substantially free of bends.Accordingly, either a flat or a square conductor may or may not bestraight. “Rectangular” as used herein is a more general term meaningflat or square, square being a special case of rectangular wherein thedimension between two opposite sides is equal to the dimension betweenthe other two opposite sides.

In the prior art motors, the wire has been cut to the desired length andstripped, then bent into a hairpin shape by hand on a one at a timebasis, then the two legs of the hairpin separated one hairpin at a timeand hand inserted into one end of a rotor or stator core, with thestripped ends of the wires sticking out of the other end of the statorbeing all bent all in one row uniformly in one direction and all in theadjacent row uniformly bent in the opposite direction so interconnectionof wires in the two rows forming a given phase could be welded, one at atime, to provide the stator windings. However in the case of stators, tobring out the connections to the phases, and to interconnect phases, thecorresponding wires needed to be re-bent to isolate them from theconnections within each phase, something again previously done by hand.

The use of the flat or square wire for the windings produces veryefficient and high power to weight ratio motors because of the greatercross-section of copper that can be put into a winding slot. However,the procedure described above is slow and highly labor intensive, andnot suitable for a mass produced motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a, 1 b and 1 c illustrate exemplary hairpin conductors used inthe present invention method and apparatus.

FIGS. 2 and 3 show an exemplary forming fixture into which the hairpinconductors are to be automatically inserted.

FIG. 4 illustrates the forming fixture having two rows of hairpinconductors with the inner diameter of hairpin conductors standing higherthan the outer diameter thereof.

FIG. 5 shows an exemplary embodiment of an overall system in which thepresent invention is used.

FIG. 6 illustrates the support of the insertion assembly in a preferredembodiment to feed the hairpin conductors to the insertion assembly whenthe insertion assembly is in either of the required two radialpositions.

FIGS. 7 a and 7 b show a face view of part of the hairpin insertionassembly and a local portion thereof taken on an expanded scale.

FIG. 8 is a side cutaway view of part of the hairpin insertion assembly.

FIG. 9 illustrates a stop to prevent the hairpin conductor from fallingout of the insertion assembly when the hairpin conductor is released.

FIGS. 10, 11 and 12 show perspective views of the hairpin conductorinsertion assembly and parts thereof.

FIG. 13 shows the push bar and the cam bar used in the insertionassembly of a preferred embodiment.

FIG. 14 shows more details of the drive for the forming fixture.

FIG. 15 shows a pneumatic actuator to drive pins from below the formingfixture to assure that each hairpin conductor is at the proper elevationonce inserted into the fixture.

FIG. 16 is a cross-section of a forming fixture of a preferredembodiment.

FIG. 17 shows the drive system for the forming fixture.

FIG. 18 shows two servo gear motors which controllably drive gearsectors in opposite directions to power the forming fixture.

FIG. 19 illustrates a populated forming fixture after twisting.

FIG. 20 shows an individual winding conductor as formed as shown in FIG.19.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description of preferred embodiments of the present invention tofollow, the terms “flat”, “square”, “rectangular” and “straight” will beused. Unless otherwise apparent, such terms are used in accordance withthe definitions thereof set forth in the prior art section above.

The purpose of the present invention is to automatically twist hairpinshaped conductors of rectangular wire as may be used, by way of example,as part of a process for automatically manufacturing motors of the typedescribed above, to form rotor and stator conductors. An exemplaryhairpin conductor may be seen in FIG. 1 a and is characterized by anoverall length L₀, formed by bending a rectangular insulated conductorwith the ends thereof being stripped of insulation over the lengthL_(S). The typical insulation on the hairpin conductors is a typicalmotor or solenoid winding insulation well known in the motor art. In apreferred embodiment of the invention, one side 20 of the hairpinconductor as formed is substantially flat up to the loop 22, with theupper portion 24 of the other side of the hairpin being bent initiallyto touch or almost touch the opposite leg of the hairpin, resulting in aslight outward bend in region 26, which together with spring back afterbending, results in the lower ends of the hairpin shape being somewhatseparated, but elastically deformable into contact with each other. Inthe preferred embodiment this is desired, as this separation, coupledwith the elasticity of the bent conductor, is used in a subsequentprocess for forming motor rotors and stators. The rectangular wire inone stator embodiment has a cross-section having a width of 4.4millimeters and a thickness of 3.0 millimeters measured over theinsulation, and is used for the fabrication of a 65 kilowatt three-phaseAC motor. Obviously these dimensions are representative of one motoronly, as the dimensions will vary depending on the motor design andpower. In the exemplary stator, the dimension L_(S) for the particularhairpin conductor illustrated is approximately 18.1 cm, though as shallsubsequently be seen, the exemplary stator uses hairpin conductors oftwo similar but slightly different overall lengths. The stripped lengthL_(S) in the exemplary stator is approximately 7.5 millimeters acrossthe width (larger dimension) of the hairpin conductors, though thestripped length across the thickness of the exemplary hairpin conductorsis slightly less. During formation of the hairpin conductors, preferablythe free ends thereof are tapered inward in both planes, as shown inFIGS. 1 b and 1 c.

The exemplary fixture into which the hairpin conductors are to beautomatically inserted may be seen in FIGS. 2 and 3. This exemplaryfixture is configured for forming motor stator conductors for a 65kilowatt three phase AC motor having four conductors per stator slot. Itis to be understood, however, that fixtures of different sizes, etc. maybe used for forming rectangular winding conductors for rotors or statorsof various size motors having the same or different number ofrectangular conductors per rotor or stator slot. In the case of theexemplary stator, there are sixty stator slots. Accordingly, in thefixture of FIGS. 2 and 3, sixty individual pockets 28, sixty individualpockets 30, sixty individual pockets 32 and sixty individual pockets 34are provided, equally spaced around different diameter circumferences,though closely spaced radially, with pockets 28 and 30 as well aspockets 32 and 34 being radially aligned with each other, at least whenthe fixture is in the position shown. In the embodiment shown, there isa thin divider between each pair of pockets. It should be noted however,that the word pockets is used herein and in the claims in the generalsense, and includes slots in the fixture parts that alone or inconjunction with the adjacent fixture part confine each of the hairpinconductor legs, both in relative rotation and translation when thefixture is energized. The different diameters on which the pockets arelocated are approximately the same as the diameters of the respectivelocations of the legs of the stator conductors in the stator in whichthe stator conductors will be used.

The hairpin conductors of the type shown in FIG. 1 a are automaticallyplaced into a respective pair of pockets 28 and 30 or 32 and 34, withthe straight side 20 of the exemplary hairpin conductor of FIG. 1 afacing radially inward in the fixture. The different diameters on whichthe pockets are located are approximately the same as the diameters ofthe respective locations of the legs of the stator conductors in thestator in which the stator conductors will be used. Also, while the legsof the hairpin conductors do not fit tightly in the pockets, but ratherslide in easily, the pockets do restrict the rotation of the rectangularconductors relative to the respective pocket. Further, as shallsubsequently be seen, because the stator slot openings at a smallerdiameter are not as far between as the stator slot openings on thelarger diameter, but the end turns at each end of the stator are thesame, the hairpin conductors to be inserted into pockets 32 and 34 areintentionally made a predetermined amount shorter than the hairpinconductors to be inserted into the outer pockets 28 and 30. Further, asshall be subsequently described in greater detail, because the hairpinconductors are initially elastically deflected when inserted into theslots, the spring back of the hairpin conductors can hold the conductorsat the elevation in the fixture at whatever elevation is set.

When substantially all of the pockets 28, 30, 32 and 34 of the fixture36 are filled with hairpin conductors 20, the fixture will appear asshown in FIG. 4, with the inner diameter of hairpin conductors standinghigher than the outer diameter thereof. Preferably the hairpinconductors in the outer diameter are slightly longer than those in theinner diameter and stand slightly higher relative to the adjacentsurface of the forming fixture than the hairpin conductors in the innerdiameter. This accounts for the diameter difference, so that once theconductors are formed, the part forming the end turns will extend thesame distance from the motor stator or rotor, regardless of whichdiameter within the slots they are placed.

Now referring to FIG. 5, an exemplary embodiment of an overall system inwhich the present invention is used may be seen. Of particular relevanceto the present invention is the hairpin forming apparatus, generallyindicated by the numeral 38, and fixture 36 positioned to receive thehairpin conductors from the hairpin 38. In that regard, it will be notedthat the hairpin conductors 20 slide down a vertically oriented sheetmetal guide 42, positioned as may be seen in FIG. 5 to deliver thehairpin conductor substantially tangentially to the circumference onwhich the pockets 28 through 34 reside. The hairpin conductors 20ejected by the hairpin forming apparatus 38 slide under the influence ofgravity along sheet metal member 42 to the hairpin insertion assembly,generally indicated by the numeral 44.

A face view of part of the hairpin insertion assembly and a localportion thereof taken on an expanded scale may be seen in FIGS. 7 a and7 b, with a side cutaway view of part thereof being shown in FIG. 8. Thehairpin conductors 20 are delivered to the insertion assembly from thelower end of member 42 and initially are held there by a finger 46 on apivoting member 48, normally held in the extended position by spring 50.The hairpin conductor 20 will freely hang vertically in this position,being sensed that it is in the proper vertical position by photo-opticaldetectors 52. Once in that position, pneumatic actuator 51 may beenergized to swing finger 46 down and out of the way, generally allowinghairpin conductor 20 to fall within the confines of the opening in theface of the insertion assembly. In that regard, as may be noted in FIG.9, when the hairpin conductor 20 is released, because of the spread inthe legs thereof, the right-hand leg as shown in that Figure will becaught by stop 54, thereby preventing the hairpin conductor from fallingout of the insertion assembly.

The fixture 36, (FIGS. 2 through 5) is mounted for accurate angularindexing in six degree increments (360° divided by sixty slots) betweenhairpin insertions. The first hairpin conductors 20 each are placed witha respective leg thereof in a respective one of pockets 28 and 30 untilthese pockets are substantially fully populated. The word“substantially” is added here, however, as in one embodiment threepredetermined pair of pockets 28 and 30 of the outer pockets areautomatically left empty because the corresponding positions in thefinal stator uses conductors with one lead having a substantiallygreater length to provide external connection to the various phases ofthe motor. In the preferred embodiment, fifty-seven pairs of pockets 28and 30 automatically become populated with hairpin conductors, with allsixty of the pockets 32 and 34 of the inner diameter getting populated.One unpopulated pocket may be seen in FIG. 19.

Now referring to FIGS. 10, 11 and 12, perspective views of the hairpinconductor insertion assembly 44 and parts thereof may be seen. FIG. 10shows the entire assembly, which is mounted on a support 56 in a mannerto provide horizontal and vertical motion of the insertion assembly. Forhorizontal motion, the assembly is mounted on rails 58 (FIG. 12) ascontrolled by actuator 60 and on vertical rails 62 (only one of which isvisible in FIG. 11) for vertical motion as controlled by actuator 64. Toproperly feed the hairpin conductor to the insertion assembly 44 whenthe insertion assembly is in either of the required two radial positionsin fixture 36, the feeder is coupled to the insertion assembly 44 andsupported on a combination of a bearing 66 (FIG. 6), allowing the feederassembly to pivot at the hairpin forming assembly 38 (FIG. 5), with thecenter of the feeder assembly being supported on bearings or wheels 68to provide a second support allowing the desired motion. In addition,the final path of travel of the hairpin conductors 20 into the insertionassembly 44 is defined by a pivoted section seen in part as section 70in FIG. 6, thereby accommodating the required vertical motion of theinsertion assembly.

To actually insert a hairpin conductor once the fixture 36 is properlyposition and a hairpin conductor is sensed as being in the properposition, actuator 51 (FIG. 8) is actuated, causing member 48 to rotateabout axis 72, swinging finger 46 down and away from the support of thehairpin 20. Also, actuator 74 (FIG. 10) is actuated, which has twoprimary functions. First, it moves push bar 76, visible in FIGS. 6 and7, though best illustrated in FIG. 13, downward and at the same time andas part of the same motion, moves cam bar 78 downward. The function ofthe cam bar 78, also shown in FIG. 13, is best illustrated in FIG. 9,namely, to force assembly 80 as a result of the force of cam bar 78 oncam follower 82 to sufficiently close the legs of the hairpin conductorso that the same will fit through opening 84 as pushed there through andinto an associated pair of a pocket in the fixture 36 (FIGS. 2 and 3).Thus by sequentially inserting hairpin conductors into the fixtures 36,the fixture may be populated as required for the particular motor orstator, except for a very limited number of hairpin conductors ofextraordinary length for phase connections in a stator assembly. In thatregard, it should be noted that the feeding of each hairpin conductorinto the fixture may be assisted in part by the ends thereof shaped asshown in FIGS. 1 b and 1 c.

Now referring to FIG. 14, more details of the drive for the fixture 36(FIGS. 2 and 3) may be seen. In the preferred embodiment, the indexingof the fixture is done through gear servomotor 86, driving coupler 88coupled from underneath to the fixture. Also in a preferred embodiment apneumatic actuator 90 drives pins generally indicated by the numeral 92(see also FIG. 15) from below the fixture to assure that each hairpinconductor is at the proper elevation once inserted into the fixture.This may or may not be necessary, as the insertion operation itself mayassure the proper and repeatable elevation. In that regard, note fromFIGS. 2 and 3 that on the fixture the pockets 32 and 34 are elevatedwith respect to pockets 28 and 30. This is to provide clearance over thehairpin conductors inserted into the outer pockets 28 and 30 whileinserting hairpin conductors into pockets 32 and 34. In the preferredembodiment, the fixture is sufficiently deep to hold the hairpinconductors at the proper elevation for the twisting operation withouthaving the ends of the hairpin conductor legs extending out of thebottom of the fixture.

FIG. 16 is a cross-section of the fixture 36 of a preferred embodimentof FIGS. 2, 3 and 4. Of particular importance to this embodiment is thefact that the outer member 94 containing pockets 28 (FIGS. 2, 3, 4 and16) is mounted for rotation, as is inner member 96 containing pockets34. The region between these two, however, containing pockets 30 and 32(FIG. 3) is rigidly attached to the base 98 (FIG. 16). The equallyspaced three holes in the inner member 96 and the three equally spacedholes in the outer member 94 (FIGS. 2 and 4) are to receive a drivesystem from above, supported to be lowered so as to engage these holeswith drive pins without contact with the hairpin conductors. The drivesystem, generally indicated by the numeral 100 (FIG. 17), includes twoservo gear motors 102 which controllably drive gear sectors 104 (FIG.18) in opposite directions. The net result of this motion is thatpockets 28 (FIG. 3) move clockwise with respect to pockets 30, andpockets 34 move counterclockwise with respect to pockets 32. This isequivalent to moving both pockets 30 and 34 counterclockwise withrespect to pockets 28 and 32, but transmits less torque to the base 98(FIG. 16). In that regard, obviously different types of drive systemscould be used, with either one of each pair of pockets being driven, oras a further alternative, retaining the member containing either pockets34 or 28, rotating the other set of pockets through twice the desiredangle, with the intermediate pockets 30 and 32 having a limitation ontheir rotation equal to half the total drive. In any event, the netresult of the twisting is shown in FIG. 19, twisting each windingconductor as shown in FIG. 20. Each of the hairpin conductors 20 is nowformed with the legs separated and joined at one end thereof by part ofthe insulated conductor which part will become part of the end turns ofthe finished motor stator or rotor. The open loop of the hairpinconductors before twisting helps avoid an excessive concentration ofbending of the insulated conductor at one location, thereby somewhatdistributing the bending and avoiding damage to the insulation layer.After forming the hairpin conductors as described, the rotatable partsof the fixture are controllably rotated a small amount in the oppositedirection to relieve the spring-back of the formed conductors. In apreferred stator or rotor fabrication process incorporating the presentinvention, the fixtures are advanced to the next station in the systemof FIG. 5 for removal and placement in a rotor or stator, after whichthe fixture is rotated back to its initial state of FIGS. 2 and 3.

While certain preferred embodiments of the present invention have beendisclosed and described herein for purposes of illustration and not forpurposes of limitation, it will be understood by those skilled in theart that various changes in form and detail may be made therein withoutdeparting from the spirit and scope of the invention.

1. A method of forming motor winding conductors from rectangularconductor wire comprising: providing a forming fixture having aplurality of pockets distributed in equal number in one or more pairs ofadjacent circles, each concentric with a center of the forming fixture,at least one member defining each of the pockets in one of each pair ofadjacent circles being rotatable, at least through a limited angle, withrespect to a member defining the pockets in the other of the respectivepair of adjacent circles; with the pockets of each respective pair ofadjacent circles being aligned with a respective radial line from thecenter, populating at least most of the pockets with hairpin shapedconductors, each having first and second legs integrally joined by aloop at one end thereof, with one leg of each hairpin conductor in arespective one of the pockets in a pair of adjacent circles and alignedwith a respective radial line; spacing the loops of hairpin conductorsin pockets for each pair of adjacent circles at a predeterminedseparation from the forming fixture for that pair of adjacent circles,either on populating the pockets or after populating the pockets; and,rotating in a first direction, relative to each other, the membersdefining the pockets in each pair of circles through a predeterminedangle, to permanently separate the two legs of each hairpin conductorwithout substantial rotation of each leg of the hairpin conductorsrelative to its respective pocket.
 2. The method of claim 1 wherein theadjacent circles have a respective diameter approximately equal to thediameter of the eventual location of a respective leg of a hairpinconductor in a slot of a motor in which the winding conductor will beused.
 3. The method of claim 1 wherein one member defining each of thepockets in one of each pair of adjacent circles is rotatable and theother member is fixed.
 4. The method of claim 1 further comprising,after rotating in the first direction, relative to each other, themembers defining the pockets in each pair of circles are rotated in asecond direction opposite the first direction through a secondpredetermined angle, the second predetermined angle being selected torelieve spring-back in the winding conductors.
 5. The method of claim 4wherein the first predetermined angle less the second predeterminedangle is equal to the angular separation between a predetermined numberof slots in a motor in which the winding conductors will be used.
 6. Themethod of claim 1 wherein the loops of hairpin conductors in pockets foreach pair of adjacent circles are spaced at a predetermined separationfrom the forming fixture for that pair of adjacent circles whenpopulating the pockets.
 7. The method of claim 6 wherein longer hairpinconductors are inserted in pockets for each pair of larger adjacentcircles than in smaller adjacent circles, and the separation of theloops from the forming fixture, of hairpin conductors in pockets foreach pair of larger adjacent circles, is greater than in smalleradjacent circles.
 8. The method of claim 1 wherein the loops of hairpinconductors in pockets for each pair of adjacent circles are spaced at apredetermined separation from the forming fixture for that pair ofadjacent circles after populating the pockets.
 9. A method of formingmotor winding conductors from rectangular conductor wire comprising:populating with hairpin shaped conductors, most of a forming fixturehaving a plurality of pockets distributed in equal number in one or morepairs of adjacent circles, each concentric with a center of the formingfixture, at least one member defining each of the pockets in one of eachpair of adjacent circles being rotatable, at least through a limitedangle, with respect to a member defining the pockets in the other of therespective pair of adjacent circles, the hairpin conductors each havingfirst and second legs integrally joined by a loop at one end thereof,the forming fixture being populated with one leg of each hairpinconductor in a respective one of the pockets in a pair of adjacentcircles and, rotating in a first direction, relative to each other, themembers defining the pockets in each pair of circles through apredetermined angle, to permanently separate the two legs of eachhairpin conductor without substantial rotation of each leg of thehairpin conductors relative to its respective pocket.
 10. The method ofclaim 9 wherein the adjacent circles have a respective diameterapproximately equal to the diameter of the eventual location of arespective leg of a hairpin conductor in a slot of a motor in which thewinding conductor will be used.
 11. The method of claim 9 wherein onemember defining each of the pockets in one of each pair of adjacentcircles is rotatable and the other member is fixed.
 12. The method ofclaim 9 further comprising, after rotating in the first direction,relative to each other, the members defining the pockets in each pair ofcircles are rotated in a second direction opposite the first directionthrough a second predetermined angle, the second predetermined anglebeing selected to relieve spring-back in the winding conductors.
 13. Themethod of claim 12 wherein the first predetermined angle less the secondpredetermined angle is equal to the angular separation between apredetermined number of slots in a motor in which the winding conductorswill be used.
 14. The method of claim 9 wherein the loops of hairpinconductors in pockets for each pair of adjacent circles are spaced at apredetermined separation from the forming fixture for that pair ofadjacent circles when populating the pockets.
 15. The method of claim 9wherein the loops of hairpin conductors in pockets for each pair ofadjacent circles are spaced at a predetermined separation from theforming fixture for that pair of adjacent circles after populating thepockets.
 16. The method of claim 9 wherein longer hairpin conductors areinserted in pockets for each pair of larger adjacent circles than insmaller adjacent circles, and the separation of the loops from theforming fixture, of hairpin conductors in pockets for each pair oflarger adjacent circles, is greater than in smaller adjacent circles.